Lipopolysaccharide-induced microglial activation induces learning and memory deficits without neuronal cell death in rats.

We used lipopolysaccharide (LPS) to activate microglia that play an important role in the brain immune system. LPS injected into the rat hippocampus CA1 region activated microglial cells resulting in an increased production of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha in the hippocampus during the initial stage of treatment. Immunostaining for IL-1beta was increased at 6 hr after LPS injection.